Manganese oxides/LaMnO3 perovskite materials and their application in the oxygen reduction reaction

Manganese-based materials can catalyze the oxygen reduction reaction (ORR), although their activity is known to depend on the crystalline phases and on the concentration of surface-active species. In the present study, we have optimized these two parameters to obtain improved catalysts for ORR. A sol-gel method was used to synthesize LaMnO3-manganese oxides composites with different lanthanum-to- manganese atomic ratios. The synthesized materials, which can be described as La1-xMnOz, were tested under ORR conditions and characterized by several physicochemical techniques such as SEM, XPS, EDX or XRD. It was found that the concentration of lanthanum governs the formation of different crystal phases and determines the crystallite size. Besides, high values of x tend to increase the surface concentration of manganese and therefore to produce more active sites for ORR. Among the materials analysed, La0.6MnOz mixed with carbon black (Vulcan) showed the best electrocatalytic performance. The high tolerance to methanol makes this electrocatalyst a promising alternative to substitute Pt-based materials in alkaline electrolytes. (c) 2022 The Authors. Published by Elsevier Ltd.

Automated summary

Manganese-based materials were optimized for the oxygen reduction reaction (ORR) by controlling the crystalline phases and the concentration of surface-active species. The synthesized LaMnO3-manganese oxides composites showed different crystal phases and crystallite sizes depending on the concentration of lanthanum. Higher concentrations of lanthanum increased the surface concentration of manganese and provided more active sites for ORR. Among the materials tested, La0.6MnOz mixed with carbon black exhibited the best electrocatalytic performance and high methanol tolerance, making it a promising alternative to Pt-based materials in alkaline electrolytes.